Method of making rotatable element potentiometer

ABSTRACT

A method of producing a potentiometer by advancing a long thin sheet of metal progressively through sets of die means at respective stations at which uniformly spaced registry holes are punched, other portions of material are punched out by each of successive die means to remove metal to commence formation of terminal means, an edge portion of the strip is thinned as by spanking to provide for formation of thin work-hardened resilient contact fingers, material removed or formed by additional die means and integral contact leaves and terminals formed, one or more contact members sheared to form at least one multi-finger contact member, the contact members and fingers bent to stand up from the strip, potentiometer housing bodies molded about portions of the strip to provide a body at each station of the strip, the upstanding contact members cupped to form respective sets of contacts, rotatable ceramic members which cermet resistive elements and slip-ring conductor sectors thereon inserted into respective housing bodies, covers applied to the bodies and ultrasonically sealed thereto, and the terminal means freed by shearing from the strip to separate individual potentiometers from the strip; and the product produced by the process.

United States Patent 1191 Primary ExaminerCharles W. Lanham AssistantExaminerV. A. DiPalma Attorney-Fritz 8. Peterson De Rouen et al. 1 May1, 1973 METHOD OF MAKING ROTATABLE ELEMENT POTENTIOMETER [57] ABSTRACT[75] In en o s: Jo ph e o n g; ell- A method of producing apotentiometer by advancing neth B. Baldwin, Corona; Henry F. a long thinsheet of metal progressively through sets of Martin, Rialto, of Califdiemeans at respective stations at which uniformly [73] Assignee: Bourns,lnc., Riverside, Calif. registry holes are punched other Portions ofmaterial are punched out by each of successive die [22] Filed: sept'1971 means to remove metal to commence formation of [21] Appl. No.:182,997 terminal means, an edge portion of the strip is thinned as byspanking to provide for formation of thin work- I hardened resilientcontact fingers, material removed [52] US. Cl...29/6l(2):9/2592/;1143239471162 or formed by additional die means andintegral com 1 1- 1m Cl 1c 17/00 tact leaves and termmals formed, one ormore contact [58] Field i976 i 0 613 412 members sheared at leastmultl'finger 29/414 3 538/164 contact member, the contact members andfingers bent to stand up from the strip, potentiometer housing [561'References Cited bodies molded about portions of the strip to provide abody at each station of the strip, the upstanding con- UNITED STATESPATENTS tact members cupped to form respective sets of con- 2173186 91939 Swartz eta] ..29/610 i i matable ceramic {neqberS which cermct3:374:536 3/1968 Schroeder et al... .....29/610 x elFmems f s 3,391,4267/1968 Hugill ..29/527.1 x thereon Inserted respectlve housmg bodles-3,402,464 9/1968 Hatch ..29/610 covers applied to the bodies andultrasonically sealed 3, 36,8 /19 K m /4l7X thereto, and the terminalmeans freed by shearing 3,597,837 8/1971 Mack ..29/6l0 from the strip toseparate individual potentiometers from the strip; and the productproduced by the process.

5 Claims, 13 Drawing Figures Patented May '1, 1973 2 Sheets-Sheet :1.

m Em Q WM v Nmi O N f YNK ww Patented May 1, 1973 2 Sheets-Sheet 2 Ll/Il l\ t METI IOD OF MAKING ROTATABLE ELEMENT POTENTIOMETER BRIEF SUMMARYOF THE INVENTION A unique single-turn potentiometer of exceptionally lowcost is produced by a unique process in which a flat strip of metal isadvanced in step-by-step uniform advances through a series of diestations at each of which a respective one of successive die operationsare performed and at the end of which operations are performed and atthe end of which operations a potentiometer'housing body has been moldedabout portions of the strip and three potentiometer contacts, eachintegral with a respective terminal member, have been integrated withthe body with the terminals protruding from the exterior of the body andthe contacts from the interior. The molded housing body at that stageremains secured to one edge portion of the strip by the three terminalmembers, which have yet to be severed from the strip. At a succeedingstation, a rotor comprising an insulative substrate of disc-likeconfiguration bearing on its lower or interior face a resistanceelement, a return conductor or collector and terminal connectionconductor means, is inserted into the body with a housing cover memberand the cover member sealed to the body to retain the rotor and seal theinterior of the housing. The substantially completed potentiometers arethereafter severed one by one from the strip by shearing adjacent theends of the terminals; and, if testing or inspection is desirable, suchfurther optional operations are performed. Either prior to severancefrom the strip or concurrently therewith, the terminal members may bebent to provide an alternative terminal configuration in which theterminals are disposed at an angle to the direction in which they extendfrom the body.

The rotor may alternatively be secured to a shaft, or may merely beprovided with other means, such as a slot, to provide for its rotationby external means. The internal contact members, at least one of whichpreferably is sheared as noted to provide a plurality of resilientcontacts, are so disposed in the housing body that as the rotor isplaced in position in the body, the sets of contacts are each engagedand resiliently stressed by a respective one of the conductors or theresistive element. Also, the housing cover, which has a central apertureinto which the shaft or other externally accessible actuating portion ofthe rotor extends, is of conformation such as to confine the rotor torotation about an axis and to a position assuring proper interengagementbetween the contacts and the elements on the inner face of the rotor.

The cover and body sections of the potentiometer housing are providedwith complementary interengaging formations which aid in properjuxtapositioning and hermetically sealing of those two parts togetherand for cooperative action in restricting rotation of the rotor to adesired extent of rotational movement. Since mechanical production ofall of the terminals and internal contacts and their fixation in thehousing body proceeds by machine operations substantially without manualoperations, it is evident that a large proportion of the cost ofassembly of the potentiometer is eliminated, and a great improvement inuniformity of the product is attained. Further, since the resistanceelement and. connections from the element and the return conductor areon the lower face of the rotor and are of cermet type, all manualoperations relating to manufacture of the rotor and its element may beperformed by automatic machinery, whereby to further decrease costs andto improve uniformity of the product.

The preceding brief summary of the invention indicates that it is aprincipal object of the invention to provide improvements inpotentiometers and a method of manufacturing the same with a view towardreducing the costs of manufacturing and improve uniformity of thepotentiometers.

Another object is to provide a potentiometer construction whicheliminates much of the labor involved in assembly of the instrument,with concurrent reduction in cost and increase in uniformity of product.

Another object of the invention is to provide a potentiometer structureof simple construction adapted for automatic machine production.

An additional object of the invention is to provide a procedure forforming respective sets of potentiometer contacts with associatedterminals as integral units of a single member of metal, formingpotentiometer bodies about the member to provide a series of the latterwith respective terminal sets and contact sets, whereby to reduce costsof manufacture and attain improvements in uniformity of the product.

Other objects and advantages of the invention are hereinafter madeevident or set out in the following detailed description of a presentlypreferred embodiment, or in the appended claims. The preferredembodiment is illustrated in the accompanying drawings.

metal strip during a series of operational steps pe'rformed in accordwith the procedure of the invention;

FIG. 2 is a lower face view of the potentiometer rotor structure usedwith the body assembly shown in FIGS. la-ld, at one stage ofmanufacture;

FIG. 2a is a view similar to FIG. 2 but at a subsequent stage ofmanufacture of the rotor;

FIG. 3 is a top face or plan view of the rotor structure shown in FIG.2;

FIG. 4 is a side view of the rotor structure depicted in FIGS. 2 and 3;

FIGS is a view similar to FIG. 3 but showing a seal member installed;

FIG. 6 is a pictorial view of the exemplary potentiometer housing cover,to somewhat enlarged scale;

FIG. 7 is a bottom view of the cover shown in FIG. 6, to approximatelythe same scale;

FIG. 7a is a fragmentary sectional view, with the sectioning asindicated by directors 7a-7a in FIG. 7; and

FIG. 8 is a pictorial view ,of a completed exemplary potentiometermanufactured according to the process or method of the invention.

Referring to the drawings generally, it may be noted that the procedureaccording to the invention involves advancing of a strip of metal inmeasured steps while at each ofa plurality of work stations or locationsthe strip in punched in various ways, portions work-hardened,

portions deformed and some removed, housing bodies molded on the strip,bending operations performed, other parts assembled into and on thebody, and completed devices severed, the strip in the meantime servingas a vehicle for the components and concurrently to provide material forsets of contact-and-terminal members. FIGS. la, lb, and 1c shown a thinflat metal strip 20 which is advanced through a plurality of die-sets instep-by-step increments or unitlengths. In the interest of conservationof space in the drawings the die-set stations will be considered to beone unit-length of strip apart, center-to-center, whereas in actualpractice the die-sets will generally be variously spaced along the strip20. The result of operations at a particular dieset station will only beportrayed as the difference between the portrayal at that station andthat at the immediately preceding station; and the stations are denotedby a respective station designation shown adjacent the strip in thedrawing, e.g., S2 for the second station. As a preliminary operation, aportion 26 adjacent one edge of the strip is thinned, as by milling orgrinding, as indicated at the right in FIG. 1a. The strip, which is ofannealed material, may be so supplied by the supplier. The thinnedportion 26 is provided for the formation of relatively thin contactfingers. Referring further to FIG. la, it is noted that at the firstdie-set station, S1, the die means operates to punch a pair of guide orregistry holes 22, 22a, and to remove a rectangular portion of materialat 24. At the next (second) die-station, S2, which as previously notedmay be spaced by a desirable distance mx from the first station (whereinm is a whole number and x is the center-tocenter distance betweensuccessive holes 22), additional punching is performed, as indicated at25.

At the third station S3, a perforation 28 is made, and at station S4 aperforation 30 is made. At station S5 a large portion of the thinnedportion of the strip is removed, leaving a window or perforation 32 anda very narrow edge portion 32a which is readily deformable. Asindicated, the strip is of annealed alloy, hence is relatively soft andeasily punched, but is capable of work hardening. At station S6,trimming operations occur, to assure precise edges at desired locations,and the remainder of window 32 is produced. At stations S6, S7, S8 andS9 the remaining finger-like portions of the thin portion 26 of thestrip, denoted 34 in station S6, are work-hardened by swaging orhammering, with some lateral expansion of the portions as indicated. Thefinger-like portions are to be formed into resilient contact members andhence they must be workhardened as noted to impart resilience to thematerial.

At a selected one of stations S7, S8 and S9 (FIGS. 1a and lb), or at aseparate station between two of those stations, an elongate aperture 36(here first shown at S7 in the interest of conservation of drawingspace) is produced; and a second of such elongate apertures, 37, issubsequently produced as shown at S8. Concurrently, or at otherintermediate die-set stations, trimming operations, such as trimming ofthe margins of apertures 24 and as indicated at 57-88, are performed.Similarly, at stations S8Sl0, the edges of material of portions 34 aretrimmed and edge portion 32a is removed. Thus at station S10 there arepresented clearly trimmed apertures 24-25, 36-37, and 28-30. At station811 a slitting or shearing operation is performed, producing a pair ofslits 38-39 between apertures 28 and 30, thus producing a middle contactfinger 40a of a set of three such fingers disposed for engagement with aresistance element. At station S12 aperture 28 is transformed, byremoval of material at both ends, into a stepped slot opening intoaperture 24, to leave outstanding a contact member 42 connected to thestrip by a base portion 42b. At station S13 a similar operation removesmaterial at both ends of aperture 30, leaving a central three-limbedcontact member 40 comprising three fingers 40a, 40b and 400, and furtherleaving a third contact member 44.

At station S14 the three contact members are trimmed at their outerends, and at station S15 (FIG. 10), the ends of the members are cuppedor dimpled to provide curved points or contacts at the extremities ofthe respective fingers 40a, 40b and 400 and at the extremities ofmembers 42 and 44. At station $16 the outer ends of the three contactmembers 40, 42 and 44 are sharply bent at right angles to the generalplane of the strip, so that they extend upwardly away from theirrespective bases. At a subsequent station, here denoted S17, stripmaterial encircling aperture 22a is removed; and at the next stationstrip material at the other side of the group of fingers is removed.Thus, as shown at station S18 there is left outstanding from the base ofthe strip an array of three legs 46, 48 and 50 each integral with arespective contact member 42, 40 and 44 and all interconnected bybridges 52 and 54 and by the remainder of the base of strip 20.

The legs 46, 48 and 50 are dimensioned and spaced to form respectivepotentiometer terminal members. The bridges 52 and 54 serve to preciselyhold in proper spatial relationship the three contact members 40, 42 and44 for the next step of the sequence of operations. At station S19 apotentiometer housing body 56 is molded about the base portions of thecontact members, leaving the upstanding contact ends thereof protrudingupwardly from the floor 56f of a circular cavity 560 formed in the body.At station S20 the up-, standing portions of the contact members arebent over in a direction away from the remaining base of strip 20 andinto angular relationship with the floor of the cavity.

As is evident, at station S20 all of the contact members are firmlyembedded, at their bases, in the material of the housing body; and henceare firmly held in proper position for engagement of their respectivecontact points by conductive or resistive elements on a rotor presentlyto be described. Further, each of the contact members is integral with arespective one of the legs 46, 48 and 50, which are designed to becomepotentiometer terminals. At a subsequently reached station, not shownbut disposed between stations S20 and S21, the interconnecting bridges52 and 54 are punched or sheared out, leaving terminal members 46t, 481and 50t supporting the housing body from the lower edge portion of strip20 as shown at station S21; At station S21 a rotor 60, which is depictedin detail in FIGS. 2a-5, is inserted into a housing cover (depicted inFIGS. 6 and 7), and the housing cover is disposed on the housing bodyand ultrasonic energy applied to seal the cover in place. As will beevident, each of the latter operations or procedural steps may beperformed at respective different stations, and the manufacture andassembly of the rotor may be effected offline in a ceramics processknown in the trade, the two sets of operations occurring in proceduresand sequences depending upon the arrangements of apparatus. Followingsealing of the cover to the housing base, the potentiometer assembly issevered from the strip by severance of the three terminal members 46!,48t and 50t between the body and the strip. As is evident, extremeuniformity of the product is attained because of the precision withwhich the components are formed, held in exact juxtaposition and somaintained during all of the forming, molding, and assemblingoperations. Also, since a minimum number of manual manipulations orassembling operations is in volved, costs are grossly reduced whileconcurrently all of the defects and troubles associated with manualoperations are avoided. Thus a much more uniform and superiorpotentiometer is produced at lower cost.

In FIG. 2 there is depicted a rotor 60 of insulati've material such asfired alumina, on the lower face of which is fired or otherwise formedan outer conductive element 60a and an electrically separate innerconductive element 60b. These conductive elements are positioned toengage contact points of members 42 and 44, respectively, and arefunctionally arranged to serve as rotor-borne slip-ring typeterminations for the rotorcarried resistance element of thepotentiometer. The upper or outer face of, the rotor 60 is depicted inFIG. 3. It is of special form, including an upstanding circularformation 60f adapted to closely fit in and be guided by a centralcircular aperture 70a (FIG. 6) formed in the housing cover 70. Theupstanding circular formation may be extended into a shaft formation ormay be short as illustrated, and forms an externally accessible meansfor rotating the rotor. The upper face of the rotor also comprises aflat circular seat 60s (FIG. 3) on which an O-ring seal 62 (FIG. 5) isseated. The O-ring bears against the inner surface of cover 70,encircling the aperture 70a and thus serving to seal the interior of thehousing against ingress of foreign material. The circular seat 60s'isextended radially outwardly to provide a stop member 60t (FIGS. 4 and 5)which is disposed to engage a complementary fixed stop abutment 70s(FIG. 7) formed on the inner wall of cover 70. Thus rotation of therotor is restricted to somewhat less than 360, as dictated by theangular dimensions of the devices 60t and 70s.

As indicated in FIG. 7a, the rotor is adapted to be held with the baseof the circular formation 60f confined in the circular aperture 70a ofthe cover with a step 60p (FIG. 3) of the upper face of the rotorbearing against the interior surface 70m (FIG. 7) of the cover, byupward pressure of shelf means 56s of housing body 56 against the lowerface of the rotor. That upward force or pressure further slightlydeforms the O-ring seal 62 to insure good sealing of the housing againstingress of foreign material. As the cover 70 is pressed into place onhousing base 56, the contacts of members 40, 42 and 44 are brought intocontacting engagement with elements 60r. 60a 60b, respectively.

To precisely position the housing cover 70 and its entrained rotorrelative to the housing base 56 as the cover assembly is applied to thebase, the latter is provided with a set of unsymmetri'cally disposedgrooves 56p and 56q (FIG. lc, station 20), and cover 70 is formed with acomplementary set of projections 70p and q (FIGS. 6, 7 and 8) whichsnugly seat in respective ones of the grooves. Preferably the ends ofthe projections are beveled or rounded whereby to aid in properplacement and registry of the cover and base as the cover is broughtinto position on the base. The cover is further provided with a sharpcircular ridge 70r (FIG. 7) (which bears against a flat surface 56m(FIG. 1c station 21) when the housing members are brought together.While the two housing members are thus in contact and held together withclamping forces, .ultrasonic energy is applied to the cover around butexteriorly of the central aperture 70a, whereby the ridge 70r andadjacent contacted portions of the body are heated and the two membersare fusion-united. In addition to the energy concentrating ridge 70r,the cover preferably also is provided with other such sharp ridgeformations as indicated at 70w, 70x, 70y and 70z (FIG. 7). While notessential to the invention, provision of the additional ridge formationsensures excellent structural union of the housing cover and body membersas the ultrasonic energy is applied. An important result is attained byvirtue of of the employment of ultrasonic vibrations to generate theheat necessary to fusionunite the housing members, in combination withthe particular structural relationship between the housing body, rotor,and housing cover. Referring to FIG. 7a, when the housing body 56 issupported as on a table or platform and an ultrasonically vibrated toolface is applied with force to the upper surface of cover 70 around, butnotupon, portion 60f of the rotor,the sharp ridge formations 70r, 70x,etc., are subjected to extreme internal stress and become hot and melt,as do those portions of body 56 which the ridge portions contact. Asfusion occurs, the cover 70 is forced downwardly to an extentapproximately equal to the height of the ridges. Thus an annular portion70z of the inner ceiling surface of cover 70, adjacent aperture 70a, islowered into forceful contact with shelf 60p of the rotor; and under'thestress of the ultrasonic vibrations that annular ceiling surface becomesplastic and isbrought into exact conformity with the surface of thenoted shelf. At the same time, the lower surface of the rotor is veryfirmly seated on the shelf 56s of body 56. Thus all differences due toallowable dimensional tolerances are eliminated, and precise fitting ofthe rotor in the housing is attained. The melted or plastic annularportion of the cover does not adhere to the rotor.

If desired, the terminal members 46t, 48! and SIM may be bent downwardlyat right angles to their dispositions as shown in FIG. 8, whereby thepotentiometer may be plugged into a circuit board or the like anddisposed for operation from above, rather than from the side. Suchbending can precede, or follow, severance of the potentiometer from thestrip 20.

As will be evident, if it be desired that the contact members andterminals be gold-plated, the strip may be passed through a plating bathbetween selected stations. Alternatively, plating may be effected as theassembly moves away from the station at which bridges 52 and 54 areremoved from between the terminals, or the entire strip may be platedprior to use. It is evident that the order in which certain steps of thedescribed procedure are performed may be inverted or otherwise altered,without significantly changing the results accomplished. Also, it isevident that certain of the procedural steps may be combined into asingle step.

Having thus described the presently preferred exemplary embodiment ofpotentiometer and method of producing the same, we claim:

1. A process for producing potentiometers, said process comprising:

moving a thin strip of electrically conductive material intermittentlythrough each of a plurality of stations at which respective apparatusesare disposed; within a first group of said stations, producingperforations at determined distances apart along the strip to providefor accurate registration of the strip relative to apparatuses and todefine unit lengths of the strip each such unit length being allocatedto a respective potentiometer, and within the group of stationssuccessively removing more material from between the first and secondedges of the strip by punching perforations in the strip; within asecond group of stations, spanking a portion of each unit length ofmaterial adjacent the first edge of the strip, to work-harden and impartresilience to those portions; further removing material from the spankedportions of the strip to produce therefrom a plurality of contactfingers each integral with the remainder of the strip; removing materialfrom the strip adjacent the second edge thereof to produce a pluralityof terminal members each integral with the strip and each integral witha respective one of the contact fingers; removing material from thestrip adjacent the second edge thereof to produce a plurality ofterminal members each integral with the strip and each integral with arespective one of the contact fingers; molding a housing body memberabout portions of the contact fingers and terminal members in respectiveunit lengths of the strip while leaving resilient contact portions ofthe contact fingers and end portions of the terminal members protrudingfrom the body member and integral with the strip;

producing rotors with conductive and resistive members thereon, andproducing housing cover members;

assembling a rotor and a cover member to respective body members; and

severing the potentiometers from the strip by shearing the terminalmembers adjacent the second edge of the strip.

2. A process according to claim 1, including the steps of dimpling theends of the contact fingers and bending the fingers away from the planeof the strip prior to molding the housing body about portions of thefingers.

3. A process according to claim 1, including the steps of shearing atleast one of the contact fingers to produce a multi-contact finger.

4. A process according to claim 1, including the steps of formingenergy-concentrating ridge means on a sealing surface of one of thehousing body and cover members, and applying pressure and ultrasonicvibratory energy to the cover member to seal the cover to the bodymember.

5. A process according to claim 4, including forming complementaryupward] facing and downwardly facmg bearing surfaces on t e rotor andthe housing body and housing cover members, and during application ofpressure and vibratory energy, forcing the downwardly facing bearingsurface on the rotor into firm bearing engagement with the upwardlyfacing bearing surface on the body member while forcing the downwardlyfacing bearing surface of the cover member into close conformity andengagement with the upwardly facing bearing surface on the rotor andcreating heat and softening the bearing surface of the cover memberwhereby under applied pressure dimensional disparities are compensatedand both pairs of said bearing surfaces are made to remain in closebearing contact.

UNITED STATES PATENT OFFICE CERTIFICATE CORRECTIUN Patent .No. 3, 729,817 I Dated May 1', 1973 Inventoflg) Joseph R. DeRouen, Kenneth BrBaldwin, Henry F. Martin It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 1, Line 10, formed and at the end of which operations are per-"should bedeleted entirely. (duplicate) Column 6, Line 7 "(which"' shouldread 'whioh [remove parentheses] Column 6, Line 22'," Y'ivrirtu e of-ofthe .s'hould mad -virtue of the-.

Column -7, Line '18, "between the first" should read -between first-.

Column 7, Lines 32 thru 35, "removing material from the stripadjacentthe second edge thereof to produce a plurality of terminal members eachintegral with the v strip and each integral with a respective one v f thtagt f ingers" should be deleted entirely C Signed and sealedthis 24thday of December 1974.

(SEAL) Attest:

MCCOY M- GIBSON JR. v 'c. MARSHALL DANN Attesting Officer Commissionerof Patents F0? powso (0459) y I. v v v I USCOMM-DC 6037B-P69 LS.GOVERNMENT PRINTING OFFDCE: I959 O-366-33 UNITED STATES PATENT ()FFIGECERTIFICATE OF CQBEQTWN 3,729,817 Dated May 1, 1973 Patent No.

lnventofls) Joseph R. DeRouen, Kenneth B. Baldwin, Henry F. Martin a Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 1, Line 10, "formed and at the end of which operations are per-"Should be deleted entirely. (duplicate) Column 6, Line 7 "(which" shouldread -which-- [remove parentheses] Column 6, Line 22,- "virtue of ofthe" should read virtue of the.

Column 7, Line 18, "between the first" should read -between first.

Column 7, Lines 32 thru 35, "removing material from the stripadjacentthe second edge thereof to produce a plurality of terminal members eachintegral with the strip and each integral with a respective one of theContact fingers" should be deleted entirely Q Signed and sealed this24th day of December 1974.

(SEAL) Attest:

icCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents USCOMM-DC ORM PO-1050 (10-69) x I n ulsfeovsnnnzur mmmm om

1. A process for producing potentiometers, said process comprising:moving a thin strip of electrically conductive material intermittentlythrough each of a plurality of stations at which respective apparatusesare disposed; within a first group of said stations, producingperforations at determined distances apart along the strip to providefor accurate registration of the strip relative to apparatuses and todefine unit lengths of the strip each such unit length being allocatedto a respective potentiometer, and within the group of stationssuccessively removing more material from between the first and secondedges of the strip by punching perforations in the strip; within asecond group of stations, spanking a portion of each unit length ofmaterial adjacent the first edge of the strip, to work-harden and impartresilience to those portions; further removing material from the spankedportions of the strip to produce therefrom a plurality of contactfingers each integral with the remaInder of the strip; removing materialfrom the strip adjacent the second edge thereof to produce a pluralityof terminal members each integral with the strip and each integral witha respective one of the contact fingers; removing material from thestrip adjacent the second edge thereof to produce a plurality ofterminal members each integral with the strip and each integral with arespective one of the contact fingers; molding a housing body memberabout portions of the contact fingers and terminal members in respectiveunit lengths of the strip while leaving resilient contact portions ofthe contact fingers and end portions of the terminal members protrudingfrom the body member and integral with the strip; producing rotors withconductive and resistive members thereon, and producing housing covermembers; assembling a rotor and a cover member to respective bodymembers; and severing the potentiometers from the strip by shearing theterminal members adjacent the second edge of the strip.
 2. A processaccording to claim 1, including the steps of dimpling the ends of thecontact fingers and bending the fingers away from the plane of the stripprior to molding the housing body about portions of the fingers.
 3. Aprocess according to claim 1, including the steps of shearing at leastone of the contact fingers to produce a multi-contact finger.
 4. Aprocess according to claim 1, including the steps of formingenergy-concentrating ridge means on a sealing surface of one of thehousing body and cover members, and applying pressure and ultrasonicvibratory energy to the cover member to seal the cover to the bodymember.
 5. A process according to claim 4, including formingcomplementary upwardly facing and downwardly facing bearing surfaces onthe rotor and the housing body and housing cover members, and duringapplication of pressure and vibratory energy, forcing the downwardlyfacing bearing surface on the rotor into firm bearing engagement withthe upwardly facing bearing surface on the body member while forcing thedownwardly facing bearing surface of the cover member into closeconformity and engagement with the upwardly facing bearing surface onthe rotor and creating heat and softening the bearing surface of thecover member whereby under applied pressure dimensional disparities arecompensated and both pairs of said bearing surfaces are made to remainin close bearing contact.